Networking Fundamentals
CCNA 1 v3 – Module 2
29/05/2016
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Networking Terminology
End-user devices provide users with
a connection to the network.
Also referred to as hosts.
Allow users to share, create, and
obtain information.
Network devices provide
transport for data between enduser devices.
Provide cable connections,
extensions, concentration.
Conversion of data formats,
and management of data
transfers
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Physical Topologies
Physical topology is the actual layout of the wire or media
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Logical Topology
Logical topology defines how media is accessed by hosts
1. Broadcast means that each host sends its data to all other
hosts on the network medium.
Non-deterministic - there is no order that the stations must
follow to use the network. First come, first served.
Example: Ethernet
2. Token Passing controls network access by passing
an electronic token sequentially to each host.
When a host receives the token, that host can send
data on the network.
If the host has no data to send, it passes the token to
the next host and the process repeats itself.
Examples: Token Ring, FDDI
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LAN  Operate within limited geographical area
 Allow multi-access to high bandwidth media
 Control network privately under local administration
 Provide full-time connectivity to local services
 Connect physically adjacent devices
MAN  Spans a metropolitan area such as a city or suburban area
 Usually consists of LANs in a common geographic area
 Example: a bank with multiple branches may utilize a MAN
WAN  Operate over a large geographical area
 Allow access over serial interfaces operating at lower speeds
 Provide full-time and part-time connectivity
 Connect devices separated over wide areas
SAN
 High-performance network to move data to/from storage areas
 Separate, dedicated network avoids traffic conflict
VPN  Private network constructed within public network such as Internet
 Access VPNs, Intranet VPNs, Extranet VPNs
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Bandwidth
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Bandwidth is limited by physics and technology
Bandwidth is not free
Bandwidth requirements are growing at a rapid rate
Bandwidth is critical to network performance
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Throughput
Throughput refers to actual measured bandwidth, at a specific
time of day, using specific Internet routes, and while a specific
set of data is transmitted on the network.
Often far less than the maximum possible digital bandwidth.
Factors that determine throughput:
 Internetworking devices
 Type of data being transferred
 Network topology
 Number of users on the network
 User computer
 Server computer
 Power conditions
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T = Time S = Size
BW = Bandwidth
P = Throughput
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Networking Models
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The historical and technical standard of the Internet
is the TCP/IP model
The U.S. Department of Defence created the
TCP/IP reference model, to design a network that
could survive any conditions, including a nuclear
war
Application layer handles issues of representation,
encoding, and dialog control.
 Transport layer deals with the quality of service issues
of reliability, flow control, and error correction
 Internet layer is to divide TCP segments into packets
and send them from any network. Best path determination
and packet switching occur at this layer
 Network Access layer (aka host-to-network layer)
concerned with all components, both physical and logical,
that are required to make a physical link
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OSI Model
• Reduces complexity
• Standardizes interfaces
• Facilitates modular engineering
• Ensures interoperable technology
• Accelerates evolution
• Simplifies teaching and learning
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The OSI reference model was released in 1984 to help
network builders implement networks that could communicate
(interoperability)
The OSI reference model is the primary model for network
communications
The process of moving information between computers is
divided into seven smaller and more manageable steps
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Presentation
Session
Transport
Network
Data-Link
Physical
DATA
SEGMENT
PACKET
FRAME
BITS
0101010101010101010
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DECAPSULATION
Application
Destination
ENCAPSULATION
Source
Application
Presentation
Session
Transport
Network
Data-Link
Physical
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OSI Top 3 Layers – Application issues
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Application
 provides network services to the user's applications
 file, print, message, database and application services
 HTTP, SMTP, FTP
Presentation
 responsible for manipulating data’s appearance as needed
by the Application layer
 Data encryption, compression and translation services
 JPEG, MIDI, QuickTime, EBCDIC to ASCII
Session
 establish and maintain communication between two hosts
 Dialogue control
 NFS, SQL, RPC, X Window
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OSI Lower 4 Layers – Data Transport issues
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Transport
 PDU – Segment
 the transport layer establishes, maintains, and tears down virtual circuits
 Windowing
 TCP and UDP
Network
 PDU - Packet
 Routing
 Data packets and route update packets
 connectivity and path selection between two hosts
Data-Link
 PDU - Frame
 physical addressing, network topology, network access, error notification,
ordered delivery of frames, and flow control
 Ethernet LCC and MAC layers
Physical
 PDU – bits
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 Cabling, standards